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Introductie van Micorosoft SQL Server 2016

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13 C H A P T E R 1 | Faster queries Nonempty calculations The number of scans necessary to retrieve a nonempty result set is reduced from many to one. Multiple measures in same table A single query now includes all measures from the same table. Measure grouping When a query requests a measure at different levels of granularity, such as Month, Quarter, Year, and Total, the query requests only the lowest-level measure value and then derives the higher-level values. Joins A storage-engine query now returns both dimension columns and measure values in the same query to eliminate redundant joins, and the order of joins now starts from the most restrictive intermediate table that correlates with the greatest number of other intermediate tables. Multiple result sets A storage-engine query now returns both dimension columns and measure values in the same query. Countrows This function is optimized to now use table heuristics. Storage-engine caching The storage engine uses one cache per database rather than one cache per server as it did in prior versions. DirectQuery is the feature in tabular models that retrieves data from the data source instead of data that has been imported into memory. DirectQuery now generates a simpler and better performing query in SQL Server 2016 than it did in earlier versions. Specifically, the query translated to T-SQL eliminates tables that are unnecessary to the results and thereby reduces the number of queries sent to the database engine. This optimization applies not only to DAX queries (which have always been supported in DirectQuery mode), but also to MDX queries, which are newly supported in SQL Server 2016. Note Now that MDX queries are supported by DirectQuery, you can use Excel to connect to a DirectQuery-enabled tabular model. If you are using Power BI or Power BI Desktop to connect to a DirectQuery-enabled tabular model, the translation to T-SQL is also improved in SQL Server 2016. The chattiness between the client tool and SQL Server has been reduced with no configuration changes required. To take advantage of this improvement, you need to restore your tabular database to a SQL Server 2016 Analysis Services tabular instance.

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